One of the victims caught in an explosion near a McDonald’s restaurant in Moscow has died of his injuries.

The 17-year-old boy died of injuries suffered when a car bomb exploded near the McDonald’s branch on Saturday lunchtime, Russian news reports said on Sunday.

Russian NTV and the Interfax news agency named the boy as Sergei Grishin.

Six other people injured in the blast remain in hospital.

Interfax reported that investigators of the Federal Security Service believed the bomb was constructed out of an artillery shell and that such devices had been found by Russian soldiers fighting rebels in the republic of Chechnya.

On Saturday, prosecutor Mihail Avdyukov said his office was investigating the bombing as an attempted murder.

He said there was no immediate evidence that the bombing was a terrorist act.

He added: “If in the course of our subsequent investigation some other information surfaces, and that depends first and foremost on the conclusions of the explosives experts, then it cannot be excluded that this criminal case could be reclassified into a different kind of crime, including a terrorist act.”

Avdyukov said the bomb could have stemmed from “possible clashes between the owners of McDonald’s and its competitors.”

The bomb car’s license plate survived the explosion, and police said they have identified the owner, a Muscovite, and are seeking to question him.

The bomb, spewing shrapnel, ripped through the restaurant’s first and second floors about 1 p.m. (0900 GMT) at the rear of the restaurant, police said, destroying several cars parked nearby.

That blast was the deadliest in Russia since the September 1999 bombings of two apartment buildings that killed 200 people.

Russia blamed those attacks on Chechen separatists and launched a military campaign in Chechnya.